What is the purpose of the underlined portion in the text about soap bubbles?

• A. It previews the next section.
• B. It provides a historical context.
• C. It lists related experiments.
• D. It describes the effects of a process that increases the longevity of the bubbles.

Answer: (D)

The main thing this underlined portion does is show the result of a technique that makes bubbles last longer. By describing what happens when the process is used, it links the method directly to a tangible benefit—the bubbles endure longer. This helps readers understand why that step matters and how it affects the outcome.

It isn’t simply hinting at what comes next, providing historical背景, or listing other experiments. It serves a cause-and-effect purpose: it explains the practical consequence of applying the process.